Field of Disclosure
The following relates generally to wireless communications, and more specifically to techniques for beam shaping at a millimeter wave base station and for fast selection of an antenna subarray at a wireless device.
Description of Related Art
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiplexing access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system).
By way of example, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communications devices, which may be otherwise known as user equipment (UEs). A base station may communicate with the communications devices on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Various communication systems may use different frequency bands depending on the particular needs of the system. For example, a millimeter wave frequency band (which may be between 30 to 300 GHz) may be used where a large concentration of UEs are relatively close to one another and/or where a relatively large amount of data is to be transferred from a base station to one or more UEs, or vice versa. Millimeter wavelength signals, however, frequently experience high path loss, and as a result, directional beam forming techniques may be used for uplink (UL) and/or downlink (DL) transmissions between a base station and a UE using millimeter wavelength frequencies. Directional beamforming techniques may enable a transmitter to transmit a signal onto a particular propagation path, and may enable a receiver to receive a signal from a particular propagation path. In this case more than one signal propagation path may exist between a UE and a base station. The reliance on directional beams, however, may make millimeter wave communications more resource-intensive.
The base station and the UE may each use multiple antennas when communicating with each other. Multiple antennas at the base station and UE may be used to take advantage of antenna diversity schemes that may improve communication rate and/or its reliability. There are different types of techniques that may be used to implement an antenna diversity scheme. For example, transmit diversity may be applied to increase the signal to noise ratio (SNR) at the receiver for a single data stream. Spatial diversity may be applied to increase the data rate by transmitting multiple independent streams using multiple antennas. Receive diversity may be used to combine signals received at multiple receive antennas to improve received signal quality and increased resistance to fading. However, in some cases, a position of the hand holding the mobile device and/or near-field effects due to the body may interfere with signals received at a plurality of antennas at the UE.